Polymorphism and priority inversion to handle different types of life style and life safety traffic in wireless sensor network for a connected home

ABSTRACT

A system including a control panel having a first and second wireless transceivers, a beacon processor of the control panel that transmits a beacon through the first transceiver, the beacon defines a repeating superframe having a first time period and a second time period, a plurality of wireless devices that exchange messages with the control panel within a respective TDMA slot of the superframe and an access processor within the control panel that dynamically adjusts a relative size of the first and second time periods to reduce or exclude WiFi access by portable user devices based upon a status of the plurality of wireless devices wherein use of the second time period is polymorphic under IEEE 802.11 and IEEE 802.15A protocols and wherein a relative priority of the first and second time periods is inverted during transmissions between the control panel and other devices of the control panel.

FIELD

This field of this invention relates to sensor systems and more particularly to networked sensor systems.

BACKGROUND

Systems are known to detect threats within secured areas. Threats may be based upon any of a number of different risks to human safety or security (e.g., fire, carbon monoxide, unauthorized intruders, etc.).

Security systems are typically based upon the use of one or more sensors that detect a specific threat within the area. The sensors may be fixed devices and/or mobile devices such as a FOB. For example, fire, smoke and/or intrusion detectors may be distributed throughout a secured area in order to mitigate damage through the early detection of fire or intrusion. The sensors can be supervised or unsupervised.

In most cases, the sensors may be monitored by a control panel. In the event that one of the sensors is activated, the control panel may activate a local audible alarm to warn occupants in the area of the threat. The control panel may also send an alarm message to a central monitoring station. A portable device, such as key fob may be used to send emergency alerts (e.g., panic alarms, medical alerts, police, etc.) to the control panel and also to send commands (e.g., arm, disarm, etc.) to the control panel. The control panel may also include a keypad and an audible siren.

In the case of industrial or public spaces, security systems may cover large areas and incorporate hundreds or even thousands of sensors. In order to accommodate such large numbers of devices, the control panel and sensors may be connected via a wireless interface.

However, security systems are often difficult to set up and use with such large number of sensors. Accordingly, a need exists for better methods of maintaining contact among the control panel, sensors and central monitoring station of wireless security systems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of a security system in accordance herewith;

FIG. 2 depicts the system architecture of multidisciplinary technologies and protocols used in a networked system such as FIG. 1;

FIG. 3 depicts a super frame that may be used by the system of FIG. 1; and

FIG. 4 depicts the wireless network topologies for sensors and WiFi devices that may be used with the system of FIG. 1.

DETAILED DESCRIPTION

While disclosed embodiments can take many different forms, specific embodiments thereof are shown in the drawings and will be described herein in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles thereof as well as the best mode of practicing same, and is not intended to limit the application or claims to the specific embodiment illustrated.

FIG. 1 is a block diagram of a security system 10 shown generally in accordance with an illustrated embodiment. Included within the security system may be one or more wireless sensors 12, 14 that monitor a secured area 16 for threats.

The sensors may be based upon any of a number of different sensing technologies. For example, one or more of the sensors may be fire, smoke or gas detectors. Some other of the sensors may be intrusion detectors. The sensors may also be provided with respective audible or visual alerting devices 15 that alert human occupants to danger. The security system may also include other wireless devices such as key fobs or keypads.

The sensors may be monitored for activation by a control panel 18 containing a radio or gateway. The control panel may be located within the secured area as shown in FIG. 1 or may be located remotely from the secured area.

Upon activation of one of the sensors, the control panel may send an alarm message to a central monitoring station 20. The alarm message may include an identifier of the security system (e.g., account number, address, etc.), an identifier of the type of sensor, a system or zone identifier of the sensor and a time of activation of the sensor.

The central monitoring station may respond by summoning the appropriate help. For example, if the sensor is determined to be a fire sensor, then the central monitoring station may summon a local fire department. On the other hand, if the sensor is identified to be an intrusion sensor, then the central monitoring station may summon the police.

All of the sensors may be coupled to the control panel via a wireless interface. In this regard, radio frequency (rf) transceivers 22, 48 within the control panel and each of the sensors may together form a portion of a wireless interface that allows each of the sensors to exchange messages with the control panel.

The security system may also include one or more wireless fobs 24 and/or wireless key pads 24 that are used to control a state of the security system (e.g., armed, disarmed, armed away, etc.). Each of the fobs may include a user interface (e.g., pushbuttons and LED indicators, etc.) and a wireless if transceiver that allows each fob to exchange control messages with the control panel. Key pads may also include a user interface (e.g., keyboard and display) and a wireless rf transceiver that allows each key pad to exchange control messages with the control panel.

Also included within the secured area may be one or more portable wireless devices (e.g., iPhones, Android devices, etc.) 26. The portable devices 26 may exchange data with one or more other devices 28 through the Internet 30 under an appropriate format (e.g., TCP/IP, etc.). As used herein, the portable devices 26 are referred to as “life style applications” while the sensors 12, 14, 24 are referred to as “life safety applications.”

The portable wireless devices 26 may exchange signals through the Internet via one or more WiFi transceivers 42 located within the secured area. The WiFi transceivers may be coupled to a local Internet service provider via home router 46 and a hardwired connection between the control panel and local Internet service provider.

Included within the control panel, the sensors, the fob and portable wireless devices is control circuitry that may also include one or more processor apparatus (processors) 32, 34, each operating under control of one or more computer programs loaded from a non-transitory computer readable medium (memory) 40. As used herein, reference to a step performed by a computer program is also reference to the processor that executed that step.

Included within the control panel may be one or more communication processors that define a super frame for communication between the control panel, the sensors, fobs and portable wireless devices.

The super frame may be defined by first and second time periods. The first time period may be divided into a number of time division multiple access (TDMA) slots that re-occur over a predetermined time period. At least some of the slots of the first time period may be reserved for use by each of at least some of the sensors and/or fobs under a 6LowPan/IPv6/IoT or IEEE 802.15.4 protocol.

The second time period of the superframe may be reserved for use by the portable wireless devices under an IEEE802.11 or WiFi protocol. FIG. 1 shows two transceivers 22, 42 (one for the 6LowPan/IPv6/IoT protocol and one for the IEEE802.11 protocol).

FIG. 2 shows a more generalized block diagram of the security system. In FIG. 2, the home router is separate from the control panel.

As shown in FIG. 2, at least some sensors 50 (of the sensors 12, 14 shown in FIG. 1) communicate directly with the control panel through the first transceiver 22 under the IEEE 802.15.4 protocol. Other sensors, such as IP cameras (shown as part of group 52 in FIG. 2) or WiFi cameras (shown as part of group 54 of FIG. 2) communicate with the control panel under an IEEE 802.11 b/g/n protocol through the home router 46. The video streams from one or more of the WiFi cameras in the network 52 can be streamed onto the display of the intrusion panel 18 via the home router. In this case, the 2.4 GHz bandwidth will be shared between sensors operating on this bandwidth using the IEEE 802.15.4/6LowPAN/IoT protocol and WiFi devices operating on this bandwidth using the IEEE 802.11 protocol.

FIG. 3 depicts an example of the super frame 100 used within the system of FIG. 1. The superframe is multidisciplinary because it supports standards such as IEEE802.15.4, 6LowPan and also facilitates coexistence with other systems such as IEEE802.11 and ZigBee bases systems. In this regard, a home router 46 operates to route messages between processors of the control panel and the FOBs and PDs and at least some of the sensors.

While the second time period is generally used for WiFi traffic, it is polymorphic in that it can also be used for IEEE 802.15.4 traffic. This will be described in more detail below.

As shown, the first time period of the super frame includes a slot 102 for a beacon, a first set of time division multiple access (TDMA) slots 104, 106, 108, 110 reserved for the exchange of messages between the sensors and the control panel and between the fob and control panel under the IEEE 802.15.4 and 6LowPAN protocol. A second set of slots 112, 114 that defines a second time period 110 of the superframe is generally designated for the exchange of messages between the portable wireless devices and the Internet under a WiFi protocol.

The frame may be embodied as a number of time thresholds distributed across the sensors and coordinators that identify the locations of various markers within the super frame. For example, the slot 102 may be identified by a starting time (i.e., zero seconds) and an ending time (e.g., 5 milliseconds). Similarly, the starting and ending times of each of the slots may be defined by their offset from the start of the super frame. In addition, the frame file may also include an identifier of the type of device allowed to use each slot as well as an indicator of the type of message that may be transmitted in any slot.

The beacon identifies a starting point of the super frame and incorporates a number of data fields defined and populated by a beacon processor. The data fields may include a first field for frame information and one or more control slots.

Each device (e.g., sensors, fobs, etc.) in the system has a short address and an IPv6 (6LowPan) address and a MAC identifier (MAC ID). The addressing system facilitates accessing of the sensors and fobs by any IPv6 compatible device under Internet of Things (IoT) concepts. This allows the sensors to be arranged by respective processors into star or tree networks as shown in FIG. 4, but not into a mesh network.

The status of the control panel (e.g., armed, disarmed, trouble, etc.) is carried as part of the beacon payload. Also, if required, a detailed indicator of panel status may be carried within respective slots under the 6LowPAN/802.15.4 protocols.

The control slots of the beacon may be used by a message processor of the control panel to send request messages from the control panel to end devices (e.g., sensors, fobs, etc.) using a unicast, multicast, or broadcast format based upon the IEEE802.15.4 addresses of the end devices.

Within the first set of slots of the super frame, a first portion 106 is reserved for alarm, status and supervision messages between the control panel and sensors. As alarms, status and supervision messages have limited data size, an IEEE 802.15.4 packet format is used by a corresponding packet processor to optimize the airtime of these messages. This protocol supports the star or tree topology needed to accommodate scenarios that demand a larger range.

In general, network information from the control panel is based upon dynamic PAN-ID and a 802.15.4 channel number for single channel operation. Sensors and/or fobs conforming with this information may enroll with the control panel automatically immediately after activation. End device commissioning of each sensor may be based upon a common secret message encryption key and an end device unique MAC-ID.

Sensors may arrange themselves into the star or tree topology including a coordinator, a repeater and one or more end devices based upon this information. Packet exchanges between parent and child devices may occur using one or more slots of portion 110, 112 and not 104, 106, 108 and 114. DNA profile transmissions (i.e., the sensor identifies what it is) and configuration transactions between coordinator and end devices may be used to facilitate the arranging of these devices into the star or tree topology.

For end devices that are too far from the control panel, the coordinator will forward the beacon.

Alarms, status and supervisory messages to the control panel may result in bi-directional communication between the coordinator and end devices. Secured encrypted communication over the air for each message may be accomplished using network keys.

Alarm messages from a sensor to the control panel may be accomplished via one of the slots of the second portion 106. In this case, the activated sensor may wake-up upon the occurrence of the event (e.g., fire, intrusion, etc.). An alarm processor within the sensor may detect the event, compose an alarm message, synchronize with its superframe beacon, identify a slot based upon the frame file and transmit the alarm message at a corresponding location within the super frame. Each slot of the TDMA super frame may include sufficient time for transmission of an encrypted packet plus enough time for a MAC level ACK message from the parent.

If a sensor does not receive an ACK message within a slot of the first portion 106, then the alarm processor of the sensor may resend the alarm message under a carrier sense multiple access and collision avoidance CSMA/CA algorithm/mechanism. In this case, the activated sensor may select a slot within one of the portions 104, 108 by first attempting to sense other users. If no other user is detected, the sensor may retransmit the alarm message to the control panel within the selected slot.

WiFi devices may operate in time period 110 to 112 and/or 114. A strobe to devices operating under this protocol may be sent based upon slot availability at the end of the super frame. Alternatively, WiFi devices may synchronize via hardwired signals.

The system of FIG. 1 operates on only a single channel. For example, life style and life safety applications can use either an overlapping or non-overlapping frequency in the same 2.4 GHz ISM band. The traffic on this channel may include audio, video, alarm data or other high volume traffic such as firmware upgrades, JPEG or web pages. This traffic is different for different types of applications and requires different bandwidths. For example, video/audio requires bandwidth in the megabyte range while alarm data only requires a few bytes.

On the other hand, the different applications sending data through the single channel have different priorities. For example, alarm data cannot be postponed and has to be sent immediately in the context of life safety. Video streaming of data from the IP cameras shown in FIG. 2 will occur in real time, whereas JPEG data will not occur in real time and can be delayed.

The latency requirements of the system are also different. For example, UL standards require that alarms be forwarded to the control panel within a few seconds. On the other hand, firmware upgrades can be postponed and can occur over a period involving many hours.

In prior art systems, a 2.4 GHz network was used for life style applications, while life safety applications where handled using a sub-GHz network (e.g., 868 MHz, 902 MHz, etc.). Hence, there was no need for prior art applications to share their bandwidth between life style and life safety applications because each had its own operating area (different frequency of operation) and dedicated bandwidths.

The superframe of the system of FIG. 1 may be dynamically adjusted during startup by discovery. For example, the first time period (i.e., the 802.15.4 time period) may be determined by a dimensioning processor based upon the number of sensors that register with the system and by a proportional number of slots that is determined based upon the registered sensors.

Similarly, the second or 802.11 time period may be determined via a discovery processor. For example, the processor may first use a discovery mechanism to determine the number of WiFi cameras in the system, then the number of 802.11 b, g, or n type cameras. Next, the processor may query the cameras to determine a set of operating characteristics (e.g., frames per second (fps), resolution, etc.). The full bandwidths of each camera may be combined to provide an estimate of the second time period. The first and second time periods may then be combined and compared to a minimum response to determine if any extra or remaining time is available. The remaining time may be used by the sensors for the retransmission of alarms.

It should be noted that the actual data transmission times of the cameras would not occupy all of the second time period since it is highly unlikely that all cameras would be transmitting simultaneously. Accordingly, a polymorphic method of use may be implemented within the second time period wherein the same time segment is used by a scheduling processor to handle different types of data. For example, the processor may temporarily (or semi-permanently) schedule a portion of the second time period for enrollment or re-enrollment of sensors over the 802.15.4 network. Similarly, the processor may reserve a portion of the second time period for other high volume traffic (e.g., JPEG, firmware upgrades to the sensors, etc.). In all cases, WiFi traffic is not allowed and the 802.15.4 traffic has a higher relative priority. While polymorphism can be viewed as the use of the second time period for 802.15.4 data, polymorphism could also be viewed as shifting the boundary between the first and second time periods.

Any of the use cases may be implemented within the system. Under one embodiment, a priority processor may control a priority of polymorphism. Under some conditions, the second time period will be used for life style applications to transmit and receive life style data. However, in case of other 802.15.4 traffic (e.g., 6LowPAN based request/response or over the air/network download (OND), all or a portion of the second time period will be stolen to be used by the 802.15.4 system.

In the case of security alarms, transmission from the control panel to the central monitoring station, the priority is inverted. In this situation, the transmission of WiFi data (which is normally given a low priority) is given the highest priority. For example, if the control panel needs to send an alarm message to the central monitoring station via a WiFi transmission, then that transmission will be given priority even over other 802.15.4 data. Similarly, if an alarm is received by the control panel from a WiFi camera, then the priority of the 802.15.4 data will be inverted and the WiFi video/audio from the WiFi camera to the control panel is given the highest priority.

In general, the system may include a control panel having a first wireless transceiver that operates under an IEEE 802.15.4 or equivalent protocol and a second wireless transceiver that operates under an IEEE 802.11 protocol where the first and second wireless transceivers can operate on an overlapping or non-overlapping radio frequency (RF) band or channel and where the second wireless transceiver occasionally provides WiFi access to portable user devices, a beacon processor of the control panel that transmits a beacon through the first transceiver, the beacon defines a repeating superframe having a first time period divided into a number of time division multiple access (TDMA) slots and a second time period for WiFi access, a plurality of remotely located, wireless devices of the control panel each having a wireless transceiver where at least some of the plurality of wireless devices exchange messages with the control panel within a respective TDMA slot of the superframe on the RF channel and an access processor within the control panel that dynamically adjusts a relative size of the first and second time periods to reduce or exclude WiFi access by portable user devices based upon a status of the plurality of wireless devices wherein use of the second time period is polymorphic under the IEEE 802.11 and IEEE 802.15.4 protocols and wherein a relative priority of the first and second time periods is inverted during transmissions between the control panel and other devices of the control panel.

Alternatively, the system may include a control panel having a first wireless transceiver that operates under an IEEE 802.15.4 or equivalent protocol and a second wireless transceiver that operates under an IEEE 802.11 protocol where the first and second wireless transceivers operate on an overlapping or non-overlapping radio, frequency (RF) band or channel, a beacon processor of the control panel that transmits a beacon through the first transceiver, the beacon defines a repeating superframe having a first time period in which messages are processed by the control panel under the IEEE 802.15.4 protocol and a second time period where messages may be processed under the IEEE 802.11 protocol, a plurality of remotely located, wireless devices of the control panel each having a wireless transceiver where each of the plurality of wireless devices exchange messages with the control panel during the first time period within a respective time division multiple access (TDMA) slot of the superframe on the RF channel and an access processor within the control panel that dynamically adjusts a relative size of the first and second time periods wherein the adjustment of the relative size of the second time period affects independent use of the RF channel by outside portable user devices based upon a status of the plurality of wireless devices wherein use of the second time period by the control panel and plurality of wireless devices is polymorphic under the IEEE 802.11 and IEEE 802.15.4 protocols and wherein a relative priority of the first and second time periods is inverted during transmissions between the control panel and other devices of the control panel.

Alternatively, the system may include a security system that protects a secured area, a control panel of the security system, the control panel has a first wireless transceiver that operates under an IEEE 802.15.4 or equivalent protocol and a second wireless transceiver that operates under an IEEE 802.11 protocol where the first and second wireless transceivers operate on an overlapping or non-overlapping radio frequency (RF) band or channel and where the second wireless transceiver occasionally and independently provides WiFi access to portable user devices, a beacon processor of the control panel that transmits a beacon through the first transceiver, the beacon defines a repeating superframe, the superframe has a first time period that is divided into a number of time division multiple access (TDMA) slots and a second time period, a plurality of remotely located, wireless sensor devices of the control panel, the sensor devices each have a wireless transceiver where at least some of the plurality of wireless devices exchange messages with the control panel within a respective TDMA slot of the superframe on the RF channel and an access processor within the control panel that dynamically adjusts use of the first and second time periods to reduce or exclude independent WiFi access by portable user devices based upon a status of the plurality of wireless sensor devices wherein use of the second time period is polymorphic under the IEEE 802.11 and IEEE 802.15.4 protocols and wherein a relative priority of the first and second time periods is inverted during transmissions between the control panel and other devices of the control panel.

From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope hereof. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims. Further, logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. Other steps may be provided, or steps may be eliminated, from the described flows, and other components may be add to, or removed from the described embodiments. 

1. A system comprising: a control panel having a first wireless transceiver that operates under an IEEE 802.15.4 or equivalent protocol and a second wireless transceiver that operates under an IEEE 802.11 protocol where the first and second wireless transceivers operate on an overlapping or non-overlapping radio frequency (RF) band and where the second wireless transceiver occasionally provides WiFi access to portable user devices; a beacon processor of the control panel that transmits a beacon through the first transceiver, the beacon defines a repeating superframe having a first time period divided into a number of time division multiple access (TDMA) slots and a second time period for WiFi access; a plurality of remotely located, wireless devices of the control panel each having a wireless transceiver where at least some of the plurality of wireless devices exchange messages with the control panel within a respective TDMA slot of the superframe on the RF channel; and an access processor within the control panel that dynamically adjusts a relative size of the first and second time periods to reduce or exclude WiFi access by portable user devices based upon a status of the plurality of wireless devices wherein use of the second time period is polymorphic under the IEEE 802.11 and IEEE 802.15.4 protocols and wherein a relative priority of the first and second time periods is inverted during transmissions between the control panel and other devices of the control panel.
 2. The system as in claim 1 wherein the transmissions associated with the inversion of the relative priority of the first and second time periods further comprises an alarm notification transmitted from the control panel to a central monitoring station of the control panel under the IEEE 802.11 protocol.
 3. The system as in claim 1 wherein the polymorphic use of the second time period further comprises a processor that enrolls or re-enrolls at some of the plurality of sensors with the control panel under the IEEE 802.15.4 protocol.
 4. The system as in claim 1 wherein the plurality of sensors further comprises at least one IP camera.
 5. The system as in claim 4 wherein the polymorphic use of the second time period further comprises a processor downloading frames of video images from the at least one IP camera to the control panel under the IEEE 802.15.4 protocol.
 6. The system as in claim 1 wherein the polymorphic use of the second time period further comprises a processor that downloads software to at least some of the plurality of sensors under the IEEE 802.15.4 protocol.
 7. The system as in claim 1 wherein the beacon further comprises a 6LowPAN protocol.
 8. The system as in claim 1 wherein the control panel and plurality of sensors further comprise a security system.
 9. The system as in claim 8 wherein at least some of the plurality of sensors further comprise fire detectors or intrusion detectors.
 10. The system as in claim 8 wherein at least some of the plurality of annunciators further comprise alarm annunciators.
 11. A system comprising: a control panel having a first wireless transceiver that operates under an IEEE 802.15.4 or equivalent protocol and a second wireless transceiver that operates under an IEEE 802.11 protocol where the first and second wireless transceivers operate on an overlapping or non-overlapping radio frequency (RF) band; a beacon processor of the control panel that transmits a beacon through the first transceiver, the beacon defines a repeating superframe having a first time period in which messages are processed by the control panel under the IEEE 802.15.4 protocol and a second time period where messages may be processed under the IEEE 802.11 protocol; a plurality of remotely located, wireless devices of the control panel each having a wireless transceiver where each of the plurality of wireless devices exchange messages with the control panel during the first time period within a respective time division multiple access (TDMA) slot of the superframe on the RF channel; and an access processor within the control panel that dynamically adjusts a relative size of the first and second time periods wherein the adjustment of the relative size of the second time period affects independent use of the RF channel by outside portable user devices based upon a status of the plurality of wireless devices wherein use of the second time period by the control panel and plurality of wireless devices is polymorphic under the IEEE 802.11 and IEEE 802.15.4 protocols and wherein a relative priority of the first and second time periods is inverted during transmissions between the control panel and other devices of the control panel.
 12. The system as in claim 11 further comprising a processor that determines a duration of the first time period and a number of TDMA slots within the first time period based upon the number of wireless devices within the system wherein a relative size of the first time period based upon the number of wireless devices within the system has a higher relative priority than the duration of the second time period.
 13. The system as in claim 12 wherein the transmissions associated with the inversion of the relative priority of the first and second time periods further comprises an alarm notification transmitted from the control panel to a central monitoring station of the control panel under the IEEE 802.11 protocol.
 14. The system as in claim 11 wherein the polymorphic use of the second time period further comprises a processor that enrolls or re-enrolls at some of the plurality of sensors with the control panel under the IEEE 802.15.4 protocol.
 15. The system as in claim 11 wherein the plurality of sensors further comprises at least one IP camera.
 16. The system as in claim 15 wherein the polymorphic use of the second time period further comprises a processor downloading frames of video images from the at least one IP camera to the control panel under the IEEE 802.15.4 protocol.
 17. The system as in claim 11 wherein the polymorphic use of the second time period further comprises a processor that downloads software to at least some of the plurality of sensors under the IEEE 802.15.4 protocol.
 18. A system comprising: a security system that protects a secured area; a control panel of the security system, the control panel has a first wireless transceiver that operates under an IEEE 802.15.4 or equivalent protocol and a second wireless transceiver that operates under an IEEE 802.11 protocol where the first and second wireless transceivers operate on an overlapping or non-overlapping radio frequency (RF) band and where the second wireless transceiver occasionally and independently provides WiFi access to portable user devices; a beacon processor of the control panel that transmits a beacon through the first transceiver, the beacon defines a repeating superframe, the superframe has a first time period that is divided into a number of time division multiple access (TDMA) slots and a second time period; a plurality of remotely located, wireless sensor devices of the control panel, the sensor devices each have a wireless transceiver where at least some of the plurality of wireless devices exchange messages with the control panel within a respective TDMA slot of the superframe on the RF channel; and an access processor within the control panel that dynamically adjusts use of the first and second time periods to reduce or exclude independent WiFi access by portable user devices based upon a status of the plurality of wireless sensor devices wherein use of the second time period is polymorphic under the IEEE 802.11 and IEEE 802.15.4 protocols and wherein a relative priority of the first and second time periods is inverted during transmissions between the control panel and other devices of the control panel.
 19. The system as in claim 18 further comprising a processor that adjusts a relative size of the first and second time periods based upon a relative level of message traffic between the control panel and plurality of wireless sensor devices wherein message traffic during the first time period has a higher relative priority over message traffic during the second time period.
 20. The system as in claim 18 wherein the transmissions associated with the inversion of the relative priority of the first and second time periods further comprises an alarm notification transmitted from the control panel to a central monitoring station of the control panel during the second time period under the IEEE 802.11 protocol. 